Silly assignments keep getting in the way of what I really want to do!

Last weekend I made the jaw 3D with some balsa wood framing which will form a structure for the skin when I eventually design it. I also realised that I hadn't posted a decent photo of the tail since it has been working in both directions. Here you can see the mechanism at the base of the tail, with two servos in opposing directions.

The whole dragon works on an interval system at the moment, where the frequency of each action is programmed and so each action is independent of the others. This also means that I can trigger actions (with the controller I will eventually build, but that's another story) so that they occur more frequently than they would naturally occur - eg. to open the mouth so that the dragon can roar on cue, or to react to movement in his environment.

As you can see when the tail starts to move the whole body has a bit of a swagger. This has two causes - firstly that the table is not even remotely flat (it's made in three sections which are all at different levels and different heights), and secondly that the body has nothing to support it to prevent swaying...

...which is where legs need to come in. Yep, legs are next.

I started tonight with figuring out the physical position of the servos - you can see the left hip in the photo. I will program the framework for how these will work so that I can see what is going on before attaching the physical legs.

The last two days have been great, so many packages arriving all at once!

From little bird electronics I got the second servo for the tail so that they would be matched. This is now installed but not yet plugged in or configured (although I have written the code already, so hopefully it works!)

More importantly, part of my order from DFRobot included a pan and tilt kit, which I have constructed and installed. Bernie can now look around - up and down as well as left and right. To do this though I had to CUT OFF HIS HEAD! Normally it is measure twice cut once, but I think this time I may have measured about 20 times. That cut would be hard to undo!

The neck now looks very mechanical, but moves very smoothly and can do so many things, I look forward to playing around with it. I will upload new video once I have it automated.

I have reached my target of having a moving tail before uni starts, and with a week to spare so now I have to decide what to do next!

dragon's spine with *new* tail

After talking about it with dad, I decided that rather than using a chain of seperate servos to move the tail, I could use just one at the base of the tail to move the whole thing. To make it curve I needed a more flexible material than MDF. In order to make it possible to change between the existing MDF spine and the new material, I decided that it would be great if the new material could also be 6mm thick. To get the flexibility at this thickness I chose to use strip rubber, which is very flexible but has enough strength at 6mm to avoid collapsing on itself. This did mean cutting the tail off the dragon, but replacing it was very easy with a couple of joining plates and bolts.

The tail is manipulated by a string attached to the servo, which passes through a series of hooks before reaching the tip of the tail. So far the tail can only wave one way - I have to buy another servo to manipulate the tail in the opposite direction, but it will operate in exactly the same way.

The base of the tail tends to get stuck on the table - it works better on a flat surface, but I will still need to smooth the bottom of the rubber as it has far too much friction and bends towards the table too much.